Proverbs 26:24-26, 28

Your enemy shakes hands and greets you like an old friend, all the while plotting against you. When he speaks warmly to you, don’t believe him for a minute; he’s just waiting for the chance to rip you off. No matter how shrewdly he conceals his malice, eventually his evil will be exposed in public.

Liars hate their victims; flatterers sabotage trust.